Coronary heart disease (CHD) is a leading cause of death in the US. Risk factors include physicial activity, which clearly is associated with lower risk. However, details regarding the association are less clear. We propose to address two unresolved issues: (1) What patterns of physical activity are associated with lower risk? (2) Do physical inactivity and overweight adversely affect CHD risk to the same degree? The Surgeon General recently recommended the accumulation of at least 30 minutes of moderate physical activity most days of the week (a pattern referred to as "lifestyle physcal activity"). This contrasts with previous recommendations that prescribe vigorous exercise for at least 20 minutes continuously 3 times a week ("structured exercise"). It is unclear whether "lifestyle physical activity" is associated with reduced CHD risk, and whether the benefit is comparable to engaging in "structured exercise." In tandem with the high prevalence of sedentary behavior, the prevalence of overweight also is high in the US, and increasing over time. Few data are available regarding whether physically active but overweight persons have comparable CHD rates as inactive but normal weight persons. Given the difficulty of maintaining weight loss among those overweight, it is important to clarify this, since such an observation would support placing much more emphasis on physical activity, in addition to traditional coronary risk factors, when assessing the risk profile of those overweight. We propose to analyze detailed physical activity data on 7,307 men free of CHD. Men have been followed for 5 years, and some 500 cases of CHD have developed. We will examine CHD risk among sedentary men, those with "lifestyle physical activity," and those engaging in "structured exercise." We also will examine CHD risk among men cross-classified by both physical activity and body weight. This proposal, at relatively little cost, will provide important information of public health significance.